The allophonic variation of liquids in American English prompted a study
examining the findings of Mann [Percept. Psychophys. 28, 407--412 (1980)],
Fowler et al. [Percept. Psychophys. 48, 559--570 (1990)], and Liberman [Speech
(1996)], who used the F3 transition as the primary cue for synthesizing [da] vs
[ga] following [al] and [ar]. The disyllables /al--da/, /al--ga/, /ar--da/, and
/ar--ga/ were recorded in a carrier sentence by two male and two female speakers
of midwestern English at three different speaking rates, and the spectra and
durations of the liquids, stops, and vowels were analyzed. Acoustic analyses
indicate structural variation: The F3 transitions of [da] and [ga] by themselves
are not stable correlates in these contexts, notwithstanding data used in
arguments for the perceptual invariance of articulatory gestures in liquid--stop
sequences. Regularities were also found: The liquids systematically affect the
F2 and F3 of the vowel in the following stop--vowel sequence, not only the onset
value of F3. In addition, each speaker encoded segments in his/her own
systematic way over variable rates, which extends Gay's findings [J. Acoust.
Soc. Am. 63, 223--230 (1978)] to tokens with coarticulatory effects. These data
will help assess alternative acoustic cues in future perceptual experiments.